Probably you learned two things about mitochondria at high school biology. First, they are cell powers. Second, you can only inherit them from your mother. However, the new study seems to overlap with this second point.
A team of researchers from the United States, China, and Taiwan identified three unrelated families with members whose mitochondria contained DNA from both parents. While this discovery may again trigger a debate about the nature of the inherited mitochondrial DNA, scientists hope to open up new ways to treat the disease.
The story began when a four-year-old patient suffering from fatigue and muscle pain was referred to the doctor-scientist Taosheng Huang at the Cincinnati Children's Hospital Medical Center. Others suggested that the boy showed signs of a mitochondrial disorder, so Huang sequenced and analyzed boy's mitochondrial DNA and found an abnormally high level of "heteroplasms," meaning that different mitochondria should contain different genes.
Thinking, sequenced the mitochondrial DNA of other boy's family members, including their sisters, parents, grandparents and siblings of their parents and grandparents. The boy seemed to have received his strange mitochondria as expected from his mother, who shared a high level of heteroplasm. But another analysis showed that his mother, grandfather and two of his big aunts inherited the mitochondrial DNA to both parents.
Huang reached out to other laboratories, looking for families with members who were similar in high heteroplasm. He found two with similar patterns where some individuals seemed to inherit mitochondrial DNA from both parents, which would then be transferred to their own children. To further remove the doubts, Huang called on Baylor College of Medicine to take independent blood samples and a sequence of mitochondrial DNA from three families. Their results confirmed Huang's results.
These results are naturally provocative, as several other attempts at demonstrating mitochondrial DNA that passed from both parents or from father to child turned out to be negative. Gizmodo has interviewed several external sources and updates the post when we hear it. It is unclear how male mitochondria would make eggs because an egg destroys sperm of mitochondria after fertilization. The new article, published in the Proceedings of the National Academy of Sciences, suggests that a possible mutation disables the elimination ability of egg mitochondria.
This study is unlikely to have a huge impact on the evolutionary time period when inheritance inheritance remains "absolutely dominant," writes the authors – an exception to the rule. But Huang was more interested in what the outcome might mean for treating the disease.
You can get acquainted with another project in which the researchers produced a baby from three parents – egg from donor, mother's core and sperm from father. This was to prevent the mother from passing on Leigh's syndrome. "It's a very complicated and costly process," Huang Gizmod explained. Perhaps, if they find a mechanism by which they could transfer father mitochondria instead of maternal, they could offer these options without three parents.
It seems that sometimes it is difficult to find solid rules in biology, even if it is the most accepted facts.[PNAS]